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9155580fd5
Instead of WAL-logging every modification during the build separately, first build the index without any WAL-logging, and make a separate pass through the index at the end, to write all pages to the WAL. This significantly reduces the amount of WAL generated, and is usually also faster, despite the extra I/O needed for the extra scan through the index. WAL generated this way is also faster to replay. For GiST, the LSN-NSN interlock makes this a little tricky. All pages must be marked with a valid (i.e. non-zero) LSN, so that the parent-child LSN-NSN interlock works correctly. We now use magic value 1 for that during index build. Change the fake LSN counter to begin from 1000, so that 1 is safely smaller than any real or fake LSN. 2 would've been enough for our purposes, but let's reserve a bigger range, in case we need more special values in the future. Author: Anastasia Lubennikova, Andrey V. Lepikhov Reviewed-by: Heikki Linnakangas, Dmitry Dolgov
110 lines
3.3 KiB
C
110 lines
3.3 KiB
C
/*
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* xlogdefs.h
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*
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* Postgres write-ahead log manager record pointer and
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* timeline number definitions
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*
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* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/access/xlogdefs.h
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*/
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#ifndef XLOG_DEFS_H
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#define XLOG_DEFS_H
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#include <fcntl.h> /* need open() flags */
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/*
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* Pointer to a location in the XLOG. These pointers are 64 bits wide,
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* because we don't want them ever to overflow.
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*/
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typedef uint64 XLogRecPtr;
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/*
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* Zero is used indicate an invalid pointer. Bootstrap skips the first possible
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* WAL segment, initializing the first WAL page at XLOG_SEG_SIZE, so no XLOG
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* record can begin at zero.
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*/
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#define InvalidXLogRecPtr 0
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#define XLogRecPtrIsInvalid(r) ((r) == InvalidXLogRecPtr)
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/*
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* First LSN to use for "fake" LSNs.
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*
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* Values smaller than this can be used for special per-AM purposes.
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*/
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#define FirstNormalUnloggedLSN ((XLogRecPtr) 1000)
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/*
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* XLogSegNo - physical log file sequence number.
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*/
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typedef uint64 XLogSegNo;
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/*
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* TimeLineID (TLI) - identifies different database histories to prevent
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* confusion after restoring a prior state of a database installation.
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* TLI does not change in a normal stop/restart of the database (including
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* crash-and-recover cases); but we must assign a new TLI after doing
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* a recovery to a prior state, a/k/a point-in-time recovery. This makes
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* the new WAL logfile sequence we generate distinguishable from the
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* sequence that was generated in the previous incarnation.
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*/
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typedef uint32 TimeLineID;
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/*
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* Replication origin id - this is located in this file to avoid having to
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* include origin.h in a bunch of xlog related places.
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*/
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typedef uint16 RepOriginId;
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/*
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* Because O_DIRECT bypasses the kernel buffers, and because we never
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* read those buffers except during crash recovery or if wal_level != minimal,
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* it is a win to use it in all cases where we sync on each write(). We could
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* allow O_DIRECT with fsync(), but it is unclear if fsync() could process
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* writes not buffered in the kernel. Also, O_DIRECT is never enough to force
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* data to the drives, it merely tries to bypass the kernel cache, so we still
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* need O_SYNC/O_DSYNC.
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*/
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#ifdef O_DIRECT
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#define PG_O_DIRECT O_DIRECT
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#else
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#define PG_O_DIRECT 0
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#endif
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/*
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* This chunk of hackery attempts to determine which file sync methods
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* are available on the current platform, and to choose an appropriate
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* default method. We assume that fsync() is always available, and that
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* configure determined whether fdatasync() is.
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*/
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#if defined(O_SYNC)
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#define OPEN_SYNC_FLAG O_SYNC
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#elif defined(O_FSYNC)
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#define OPEN_SYNC_FLAG O_FSYNC
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#endif
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#if defined(O_DSYNC)
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#if defined(OPEN_SYNC_FLAG)
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/* O_DSYNC is distinct? */
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#if O_DSYNC != OPEN_SYNC_FLAG
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#define OPEN_DATASYNC_FLAG O_DSYNC
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#endif
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#else /* !defined(OPEN_SYNC_FLAG) */
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/* Win32 only has O_DSYNC */
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#define OPEN_DATASYNC_FLAG O_DSYNC
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#endif
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#endif
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#if defined(PLATFORM_DEFAULT_SYNC_METHOD)
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#define DEFAULT_SYNC_METHOD PLATFORM_DEFAULT_SYNC_METHOD
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#elif defined(OPEN_DATASYNC_FLAG)
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#define DEFAULT_SYNC_METHOD SYNC_METHOD_OPEN_DSYNC
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#elif defined(HAVE_FDATASYNC)
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#define DEFAULT_SYNC_METHOD SYNC_METHOD_FDATASYNC
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#else
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#define DEFAULT_SYNC_METHOD SYNC_METHOD_FSYNC
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#endif
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#endif /* XLOG_DEFS_H */
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